It is as easy to install a turbo on the 240D engine as it is to destroy the engine as a result.

The 300D turbodiesel engine was very different from the naturally aspirated engine in several ways (now don't quote me on everything, because the turbodiesel was never available in my country):

1. The turbodiesel uses a different oil pump. Your engine uses an oil pump driven off the timing pulley which also drives the vacuum pump and injection pump. The turbodiesel uses a pump driven off a chain on the crankshaft. This pump is similar to later diesel engines, and I assume that it has a better flow rate.
2. The turbodiesel block has provision to feed oil to the turbo.
3. The turbodiesel has a different oil spray(?) system to aid in the cooling of the pistons.

The turbodiesel's pistons and con-rods have different part numbers to the naturally aspirated engines. I can't tell what the differences are, but different part numbers mean that there must be differences.

If you can solve the oil supply situation, I suppose you could install a low boost turbo. But I wouldn't.

 

I know AMG did a turbocharged OM616. But I don't know the extent of the work required. Maybe they used modified OM617 turbo parts (such as oil sprayers), maybe they fitted a bigger oil pump, or maybe they just slapped a turbo on.

Still, if you really need a bit more power, consider installing an OM617, NA or turbo.

 

The parts will not fit, they are 5 cylinder and you have 4. At the least you would need to cut and weld the 5th cylinder off the intake and block the 5th cylinder exhaust port (and you will not be able to bolt to the last manifold stud).
In addition, the turbo is sized for a larger engine so overall performance would be very poor.

If you want more power, the only two cost and time effective options are to swap the drivetrain or swap cars.